Lake Billy Chinook (Jefferson)

(From Atlas of Oregon Lakes, Johnson et al. 1985). Lake Billy Chinook (also known as Round Butte Reservoir) is the uppermost of two Portland General Electric reservoirs on the Deschutes River. It is located about 100 miles above the confluence of the Deschutes with the Columbia River. Round Butte Dam was completed in 1964 by P.G.E. for hydro-electric power generation. It is an earth and rockfill structure 440 feet high, designed to hold 535,000 acre feet of water and to generate 300,000 kw of electric energy. The dam is named for Round Butte, a prominent topographic feature rising directly to the east. The name Billy Chinook is in honor of a Wasco Indian who joined the John C. Fremont expedition in 1843 and eventually accompanied the explorer to Washington D.C. Billy Chinook later became one of the nominal chiefs of the Dalles band of Wascos and in this capacity was a signer of the "Treaty with the Tribes of Middle Oregon, 1855".

The lake is a very busy recreation site. A huge state park, Cove Palisades, sits astride the Deschutes River and the Crooked River Arms. Several boat launching ramps, a swimming beach, and camping and picnicking sites are available in the park and all receive very heavy use. Angling is good for a variety of species. Rainbow trout are stocked heavily and are taken in good numbers as are other trout species such as Dolly Vardon and brown trout. Kokanee angling has also become quite successful following a stocking program in the 1970s. Power boating and water skiing are favorite pastimes during the warm summer months.

The large impoundment drains the entire Deschutes River basin above Round Butte Dam, an area of 7380 square miles ranging from semi-arid rangeland to the forested crest of the Cascades. The lake itself consists essentially of three long, narrow arms where water behind the dam backs up into the Metolius, Deschutes, and Crooked Rivers. The Metolius arm is 12 miles long and contributes 40 percent of the inflow; the Crooked River arm is six miles long and also contributes 40 percent of the inflow; the Deschutes arm is 8.5 miles long and provides the other 20 percent of the inflow. Much of the limnological character of the lake depends upon the water quality characteristics of each river. In general, the Metolius river which drains forested terrain to the west, supplies water which is cooler, lower in dissolved minerals, and much less turbid. The Crooked River drains an area with extensive pasture and agriculture land. Water from this drainage basin contains a higher concentration of dissolved minerals, is warmer in the summer, and frequently carries a substantial load of silt. The Deschutes River water is generally intermediate in character and receives the greatest influence from human development. Each major inlet contributes relatively high concentrations of major ions to the lake. Much of the drainage basins of the Crooked and Deschutes Rivers are in semi-arid climates where evaporation concentrates the major ions, and the main source of Metolius River water is from ground water which contains high concentrations of major ions. Similarly, phosphorus concentrations are high in the inlets (including the Metolius) and throughout the entire lake.

Water transparencies in Lake Billy Chinook are influenced primarily by the amount of sediment entering the lake from the three rivers, and less so by the densities of phytoplankton. The lowest transparency value in this survey of 3.6 feet (1.1 meters) was recorded in the Crooked River arm, followed by 6.6 feet (2.0 meters) near the dam, 8.5 feet (2.6 meters) in the Deschutes arm, and 19.7 feet (6.0 meters) in the Metolius arm. In contrast, the highest value recorded by Mullarkey (1967) was 40 feet (12.2 meters) in the Metolius arm; his lowest was 0.3 feet (0.1 meters) in the Crooked River arm. Seasonally, water transparency was lowest in the spring in the 1982 survey: a value of 6.6 feet (2.0 meters) was noted at the sample site behind the dam on 5/21/82, in comparison to 14.8 feet (4.5 meters) in summer, and 13 feet (4.0 meters) in autumn. Dissolved oxygen in the reservoir ranges from 0 to super saturated (maximum observed D.O. was 16 ppm). The lowest dissolved oxygen occurs in the silt laden hypolimnion of the Crooked River arm. In the epilimnion, and in the Metolius arm in general, dissolved oxygen remains at 6ppm or higher, more than adequate for salmonid fish. The lake stratified in the summer of 1982, with a thermocline at about 23 feet (7 meters). The surface water temperature reached 70 degrees Fahrenheit (21 degrees Celsius) at this time, favoring water skiing and swimming activities. During stratification, only a moderate depletion of hypolimnetic dissolved oxygen occurred.

The phytoplankton species clearly indicate eutrophic conditions; however, their densities are lower than might be predicted from the high nutrient concentrations and warm water temperatures. The predominant algal species (near the dam) during the spring were eutrophic diatoms(Stephanodiscus, Asterionella, Fragilaria) and the flagellate Cryptomonas. During summer, a light bloom of Aphanizomenon was visibly present, but was neither objectionable nor a deterrent to water contact sports. Phytoplankton samples were collected from sites near each major inlet (within the reservoir) in May 1982. Each sample, although similar in that each consisted of periphytic algae (algae growing "attached" to a substrate), contained a different assemblage of algal species. The algae near the dam were different from the algae at each inlet, and contained true planktonic species. Macrophytes are scarce in Lake Billy Chinook due to the very steep littoral areas and the rocky substrate. Overall, the trophic state of this lake is eutrophic, but at the lower end of the spectrum. Because of the basin morphometry (steep shores and large volume), and because the phosphorus concentration is already quite high, it is unlikely that future increases in recreational activities would adversely affect the water quality.

The list below includes results of zebra and quagga mussels surveys conducted by the Center for Lakes and Reservoirs and other agencies. The results "non-detect" and "results pending" indicate that surveys for zebra and quagga mussels were conducted, but none were detected or results are pending. For more details on zebra and quagga mussel monitoring, please visit the Online Mussel Monitoring Map.

Date

Status/Species

Source

Aug. 30, 2013

non detect

Portland State University

Aug. 2, 2013

non detect

Portland State University

Sept. 14, 2012

non detect

Portland State University

Aug. 21, 2012

non detect

Portland State University

Sept. 2, 2010

non detect

Portland State University

Sept. 2, 2010

results pending

Portland State University

Aug. 10, 2010

results pending

Portland State University

The list of plants below includes results of aquatic plant surveys conducted by the Center for Lakes and Reservoirs as well as aquatic invasive plant species detections that have been reported to iMap Invasives: an online, GIS-based invasive species reporting and querying tool.

Plants listed in the table below are categorized as native to Oregon, on the Oregon Department of Agriculture’s (ODA’s) Noxious Weed List, on the Federal Noxious Weed List, or non-native but not listed as noxious. Federal Noxious Weed List plants are plants determined by USDA to be serious threats to U.S. agriculture, irrigation, navigation, public health or the environment (7 C.F.R. 360.200). The ODA Noxious Weed categories are:

ODA Class A - weeds either unknown or with small enough infestations to make eradication or containment possible; targeted for eradication or intensive control.